Elastic locking insert secured by thread rolling



H. T. BURDICK 2,663,344

ELASTIC LOCKING INSERT SECURED BY THREAD ROLLING Dec. 22, 1953 Filed July 2, 1952 FIG.3.Y

FIG. 2

Patented Dec. 22, 1953 READ ROI-LINE Hugh '1: Burdick; Chicago, 111%,;assignortutlllihok:

TooL Works, Chicago; 111;,

at corporation of Application .1 2 ,}.1952, 295,185,

Glivimsr (Cl. Mi -7 The present inventionv relates to selfqocking. rotary fasteners, such as; bolts, screws; stujdsand the like, and" more specifically relatesv to the i'm provement ofalocking, bolt; screw; or'studiwhich has an insert which effectively locks such devices reiative to a complementarythreadednnt or equivalent against inadvertent loosening.

study oflocking"; screws now presently'being commercialized, as weli'. various devices of this typewhich have been patented" previously, indicatesthata good many ofthes'e devices cone template an article which, from the standpoint. of manufacturing; is diificult or impracticable. My'study-a'lso indicates.v that n ianv'oi. these devices. are aIso of. such. a; nature that the shank of the fastener ismat'eriallY weakened in ordeiz to provide the locking element with its, desirahie;

in the shoulder which. retains the. locking insert. 7

properly positioned is formed. during; the thread: rolling. operation so. that. the. permanent. assem-- big. of the. locking. insertin the. shank. of: thee fastener accomplished. without. the necessity ot a secondary-stakingoperatiom I It isv stillv another object of the. invention to. provide. a. rocking screw. whi'cin. by reason: of proper selection. of. materiaLusedto; formvthe.

locking. insertretains itsrefiectiveness after long continued.- or repeatedzmse.

It still. another object..- otthe invention: to

provide amethod for. producing the fastener:

contemplated. by this invention. whicht assnres; economy inthe manufactureot. the devicewhich:

islaccomplished without theuse of a speciaimaechine.

Various... other obi acts; and advantages: will.v be

come. apparent. byreferenceto; the; fOHDWi-Hg de scription. and accompanying; drawings. wherein:

Fig, 1. is. a. perspective viewrof a'jocking; screw incorporating, the invention; contemplated; here.--

Fig. 2*15: arsiidejeIevationai view, partlyv in sectiom of a screw; blank. with. the. locking, insert mounteditherein.;

Fig, 3' is aside el'evationalv view; partly, in. sec- Fig. 4: isiai.crnsssectionaliview taken along. the line m-'-4:inms. 2;,

Fig; 5' a cross..sectiona11'view taken along, the Iin'e.5-5 in: Fig. .3; f

Fig. 6'' is.v a; cross sectional, view showing. the first, step, inthe manufacture. oi a, Inching bolt ofthetype contemplated Iiv "the, invention herein, wherein. a. recess; is, provided in: the; shank oi: the

screw;

Fig. 7 is a cross sectional; View, of a screw blank and. shows, one method;o;'feeding..a..p1astic, insert. throughthe aperturev provided. for ac.- commodating, same; I

.Fig... 81 is a. cross sectionaLview of. a. fastener showing;- the cutting; of! the; locking. insert to proper,

Eigsill is..a.side-.-view. ofla locking, screw incorporatingg. the. inventioncontemplated.herein; during the. thread; rolling. process. which. is accompl'ished. by meansF oi. conventionah rolling; dies,

Eig LIL showsstill'; another; embodiment. of the im entiom. wherein. a. locking; screw. insert is mountedi 'nialsiot adjaeentthe end oi, the screw shank; and, also, proper. position. in the samemanner as the embodimentsshown. above Eig 1 1 isa. erossiseotional viewot the fastener shown. in 10 taken,- along the line Li-J-l Ei-g 1&2 is a,- longitudinaI-viem of the fastener shown in- Fig 115i-v along the line. l2- i2; Eig;v 13 mat side elevationaflt view, partly ill-.599. tion showing as locking; insertof? the type con.- tempiated: by the invention: herein f disposed: at antacute anglee re1ative-:to-.the,axis-.o1 the screw member; and:

Fight: an view. anothen embndimenti.- wherein th insert. is 1ocated to one; side theiongitud'lnal' axis; of

thezfastenen I I Referring: nowto; the wings wherein; like numerals are; nsect. denote; corresponding parts; Figs 1 shows; a;. Locking; screw designated;

, generallyb n the numeral;- l flsi oomprisedzof: a; head l2, a shank portion I 4, whichzshank portion is provided. with am apertures ifiz" adapted to accome mod-ate; a. plug; of. resilient: material; 143;: such re.- silient; materiali being" ants oi. the; well. known pl'astizsmaterialsrsuchasznylon;Qrlomet-cetera. Tl-1e. materialg usedv in;- the'; fabricatiom the plug. I18; preferably" has.as"resilient; characteristic,

. as. whiclmhamcteristicdspresent: oven long-z: penc ls similar son s and shows- 3 of time, and is not materially affected in the temperature ranges for which the locking screw might be subjected, and which has such other features as being inexpensive, easy to Work with, et cetera, which are so essential in the mass production of such devices.

A very important aspect of the invention contemplated herein resides in the method contemplated to be used to secure the insert element [8 within the confines of the screw shank [4. It is contemplated that these locking inserts can be adequately mounted by subjecting the screw blank It with the insert l8 mounted therein, as shown in Fig. 2, to a thread rolling operation. The thread rolling process not only. forms the helical threads 19 on the shank of the screw, but at the same time swages the material 20 of the shank l4 adjacently positioned to the periphery of the plug into impinging relation therewith, and at the same time compresses the plug forming at least partial screw "threads 2| in theend faces thereof. Subsequent to the thread rolling operation, and dependent upon the length of the plug !8 mounted in the stud shank, a predetermined amount of material will extend beyond the valleys and crests of the surrounding threads' formed on the screw blank. By predetermining the amount of material desirable to extend be yond the crest of the screw threads, the locking effectiveness of these locking faces is determined method, and the apparatus to be used with that method, to make the locking screws contemplated by this invention. 1 In Fig. 6, the screw blank It has been fed into a fixture 22 which is provided with aperture 24 designed to accommodate the shank of the fastener l0. Ports or entry holes 26 and 28 are provided and are aligned relative to each other andpreferably arranged to enter the cavity24 at diametrically opposite sides thereof. Note in Fig. 6 that an insert 39 has been provided to form a hole through which drill bit 32 enters the cavity 24. On rotation of the bit, the desired size of hole may be made in the fastener shank and the bit thereafter withdrawn. In Fig. 7, the next step is shown wherein the supply of locking insert material, such as rod 34, moved inwardly into the prepared hole of the fastener shank until it extends through the screw blank a predetermined distance. Preferably, the rod 34 is advanced until its terminal end 35 extends slightly beyond the wall portion 35 and the aperture 24 and into the drill hole 26, as shown in Fig. 7. It should be noted, in Figs. 6, '7, and 8, that the dimension of the aperture 24 is greater in cross section than the diameter of the fastener shank. This difference used and the l4 and the adjacent wall portion 48 of the fixture 22. At the same time, the terminal end of the rod 34 is sheared from the insert 13 by the lower edge of the Wall portion 36 of the aperture 24. Thus, the insert I8 is cut to an exact predetermined length.

The fastener blank, with the insert, mounted therein, is now fed through any conventional type of thread rolling machine, which may include thread rolling dies 4| and 42, as shown in Fig. 9. The rolling action deforms the material 20 of the shank l4 surrounding the openings of the aperture I 6, so that the material 23 is formed into projections which extend into the insert l8 and lock it in place. This rolling action which forms the helical threads E9 on the screw shank M at the same time forms the thread segments 2! on the ends of the insert It. It should be noted that the length of the insert it is greater than the diameter of the shank M, and since the material of the insert is resilient, the thread segments 2! of the insert extend radially outwardly of the threads l9. In other words, the outer diameter A of the threads i9 is less than the outer diameter B of the thread segments 2|, as shown in Fig. 3. Furthermore, the

In Fig. 8 is shown the last step in the method designed to prepare this fastener for the thread rolling operation. Fastener I0 is removed from the fixture 2-2 by knockout pin 38, said removal by the pin serving to shear off the locking insert l8 from the rod 34 by reason of the shearing action of the outer surface or the fastener shank bottoms of the thread segments 2| extend radially outwardly from the bottoms of the threads I9 on the screw shank. Thus, the resilient thread segments 2| will effectively engage the threads of a complementary threaded fastening device, not shown, to lock the screw H] against inadvertent loosening. Upon completion of the thread rolling operation, the device is ready for use. The formation of the thread segments 25 on the ends of the insert l8 makes the application of the fastener l0 toa threaded nut or the like relatively easy since it is only necessary for the threads of the nut to compress the insert and not to cut through it as in a case where the insert is not formed with thread segments. Moreover, the forming of thread segments on the insert eliminates the possibility of material being cut from the insert and jamming the threads of the fastener I 0 during its application to a complementary fastener element such as a nut.

By reason of the thread rolling operation extruding the metal of the stud inwardly in the vicinity of the marginal edge of the aperture Iii in the fastener, the staking operation which would normally be necessary to secure the looking insert is eliminated.

In Figs. 10, 11, and 12, I show still another form of the invention, wherein a screw it?) is provided with a slot 44 adjacent the end opposite the head of the fastener and a locking insert I81) of suitable'size mounted therein. This insert, similar to the insert described in the embodiment shown in Figs. 1 to 5, inclusive, has an over-all measurement greater than the length of the slot 44 so that when the thread rolling operat1on is performed, a predetermined amount of the material of the insert extends beyond the threads of the screws threads. It should be noted that the shoulders 28b extend inwardly to impinge upon the locking insert where the threads I of the screw blend into the threads of the looking insert, and, in addition, that during the thread rolling process, portions 45 of the shank at the extremity thereof and adjacent the locking insert are swaged inwardly to trap the insert E82) and preclude axial movement of the insert rela tive to the screw shank. In order that deformation of the plastic locking insert i829 is permitted during the thread rolling operation, in some instances, I have found it advisable to provide a space 48 behind the insert so that during the thread rolling operation displacement of the insert is permitted and'compression of the insert can be controlled. This space may be provided by forming the slot 44 with a concave wall, as shown in Fig. 12, or alternatively by forming the insert with a concave inner edge.

In Fig. 13, I show a locking screw Hlc, wherein the locking insert I80 is disposed at an acute angle relative to the longitudinal axis of the screw which has the obvious advantage of producing locking surfaces 50 and 52 which are axially spaced each from the other along the shank, so that the locking effect may be obtained for a greater distance along the length of the screw shank. Another advantage of the device of Fig. 13 is that the axial spacing of the locking surfaces 50 and 52 tends to tilt or cock 7 threads of the screw and the threads of the complementary fastener. Furthermore, because the surfaces 50 and 52 are disposed at an angle to the axis of the insert !8c, the area of these looking surfaces is increased without weakening the screw by increasing the size of the aperture into which the insert I30 is placed. The portions 200 of the screw shank may be extruded as described above to retain the insert I80.

I also contemplate that where an increase in the amount of locking surface of the insert is advantageous, the aperture provided in the screw shank for accommodating the insert can be located at one side of the diameter of the screw. This structure is shown in Fig. 14, wherein the insert 18d is located at one side of the longitudinal axis of the fastener shank Md. By this arrangement, the opposite openings in the external wall in the screw have a larger cross sectional area than the cross sectional area of the hole itself when determined mathematically by the formula M and, thus, the area of the ends or looking surfaces of the insert [801 is larger than the diameter of the insert. This has the obvious advantage over enlarging the size of the aperture drilled in the screw in that the desired increase of locking surface can be provided without weakening the shank of the screw. Furthermore, by locating both locking surfaces or ends of the insert l8d on one side of the center line of the shank [4d, the insert which will engage one side of a complementary fastener, not shown, will tend to force the shank against the opposite side of the comlementary fastener and, thereby, increase the frictional resistance between the threads of the shank and the threads of the fastener. As before, the portions 28d of the shank are extruded during the thread rolling operation to retain the insert.

From the foregoing description, it is seen that the present invention has provided a simple, yet highly efficient self-locking fastener which may be rapidly and economically manufactured. Moreover, the novel method set forth herein makes it possible to form the thread and secure the insert in one step, which not only has the obvious advantage of eliminating the conventional secondary staking operation, but also eliminates the possibility of damage to the threads which might occur during such a secondary staking operation.

While specific embodiments of the invention are hereinabove described and shown, it is to be understood that I do not intend to be limited to the constructions and methods illustrated and,

described, but limited only by the following claims.

I claim:

1. A self-locking rotary fastener including an elongated shank having rolled screw threads on a peripheral surface thereof, said shank having a recess therein opening at said peripheral surface so as to intersect thread convolutions on said shank, and an insert of deformable material mounted within said recess and presenting an exposed locking section for lockingly engaging complementary thread convolutions, said locking section comprising pre-formed impressed thread segments, each locking portion of which normally extends radially outwardly with respect to corresponding portions of the adjacent screw thread convolutions and providing helical continuations of said convolutions, and means for securing said insert against dislodgment from said recess comprising material of the shank periphery defining the entire mouth of the recess converging to restrict the size of said opening, said material resulting from thread rolling and impingingly encircling the periphery of said insert.

2. A self-locking rotary fastener as set forth in claim 1, wherein the recess which accommodates the insert completely traverses the screw shank to provide a pair of peripheral locking sections.

3. A self-locking rotary fastener as set forth in claim 1, wherein the recess which accommodates the insert extends transversely of and at an acute angle to the axis of the screw member so as to increase the exposed peripheral area of the insert.

4. A self-locking rotary fastener as set forth in claim 1, wherein the recess which accommodates the insert extends transversely of the screw shank and substantially laterally with respect to the screw axis so as to increase the exposed peripheral area of the insert.

HUGH T. BURDICK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,519,126 Furlan Dec. 16, 1924 2,224,659 Stoll Dec. 10, 1940 2,539,887 Boots Jan. 30, 1951 2,608,229 Brutus Aug. 26, 1952 FOREIGN PATENTS Number Country Date 372,405 Great Britain May 9, 1932 496,638 Great Britain Dec. 2, 1938 

